1. Field of the Invention
The present invention relates to a hermetic compressor, and more particularly to a connecting rod for a hermetic compressor capable of converting the rotation of a crankshaft into the reciprocating linear motion of a piston.
2. Description of the Prior Art
FIG. 1 is a sectional view showing the internal construction of a hermetic compressor according to the prior art. Referring to the drawing, a frame 2 is positioned inside a hermetic container 1, which includes upper and lower containers 1t and 1b. A stator 3 is fixed to the frame 2, which is supported inside the hermetic container 1 by a spring 2s. A crankshaft 5 is positioned so as to extend through the center of the frame 2. A rotator 4 is integrally formed on the crankshaft 5 and is rotated together with it by electromagnetic interaction with the stator 3.
The crankshaft 5 has an off-center pin 5b positioned on the upper end thereof while being offset from the rotational center of the crankshaft 5 and a balance shaft 5c positioned opposite the off-center pin 5b. The crankshaft 5 is rotatably supported on the frame 2. A crankshaft connecting portion 9c of the connecting rod 9 is fitted to the outer peripheral edge of the off-center pin 5b so as to rotate relative to the edge while a sleeve 8 is press-fitted and interposed.
The crankshaft 5 has an oil passage 5a formed therein, through which oil L is guided from the bottom of the hermetic container 1 to the top of the frame 2 to be scattered, and a pumping mechanism 5d positioned on the lower end of the crankshaft 5, in order to pump the oil L into the oil passage 5a. 
The frame 2 is provided with a cylinder 6, which has a compression chamber formed therein. The compression chamber contains a piston 7, to which the piston connecting portion 9a of the connecting rod 9 connects. The cylinder 6 has a valve assembly 10 positioned on the upper end thereof, in order to control the flow of a refrigerant into/out of the compression chamber. A head cover 11 is mounted on the valve assembly 10, and an intake muffler 12 is positioned on the head cover 11 while connecting to the valve assembly 10, in order to transmit the refrigerant to the compression chamber.
In the drawing, reference numeral 7a refers to a pin fitted to the inner peripheral edge of the piston connecting portion 9a so as to fasten it to the piston 7, and 9b refers to the body of the connecting rod 9.
The construction of the connecting rod 9 is shown in FIG. 2 in more detail. The sleeve 8 is press-fitted to the inner peripheral surface of the crankshaft connecting portion 9c. The inner diameter of the sleeve 8 is determined in such a manner that it can rotate relative to the off-center pin 5b. 
However, the conventional hermetic compressor has the following problems.
As shown in FIG. 2, the sleeve 8, which is press-fitted to the crankshaft connecting portion 9c, deforms due to the limited space of the inner peripheral edge of the crankshaft connecting portion 9c. Particularly, the inner peripheral surface of the sleeve 8 deforms, i.e. protrudes irregularly, and varies the inner diameter.
More specifically, part A of the sleeve 8 is enlarged and shown in a separate graph in FIG. 2 with a scale of 1 micron. In the graph, the straight solid line indicates enlarged part A of the sleeve 8, before being press-fitted, and the wavy solid line indicates enlarged part A of the sleeve 8, after being press-fitted. It is clear from the graph that the wavy solid line has a maximum distance of about 6 micron from the straight solid line. This implies that the entire inner diameter of the sleeve 8, including part A, has similar deformation.
If the inner diameter of the sleeve 8 deforms as shown in FIG. 2, the sleeve 8 inevitably makes linear contact with the off-center pin 5b, which is inserted therein. As a result, a vanishing phenomenon occurs on a surface treatment layer of the inner peripheral edge of the off-center pin 5b, and the frictional force between the sleeve 8 and the off-center pin 5b increases. This degrades the efficiency of power transmission from the crankshaft to the connecting rod 9.